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UID:35@atst.osups.universite-paris-saclay.fr
DTSTART;TZID=Europe/Paris:20241205T140000
DTEND;TZID=Europe/Paris:20241205T170000
DTSTAMP:20241204T112914Z
URL:https://atst.osups.universite-paris-saclay.fr/calendrier/soutenance-de
 -these-nina-bizien-5-decembre-2024-a-14h00-au-lpc2e-orleans/
SUMMARY:Soutenance de thèse Nina Bizien - 5 décembre 2024 à 14h00 au LPC
 2E-Orléans
DESCRIPTION:Annonce transmise par Nina Bizien (LPC2E)\n\nHi everyone\,\n\nI
  am pleased to invite you to my PhD defense\, which will take place on Thu
 rsday 5th December in the Amphithéâtre Sadron at the LPC2E\, Orléans. T
 he defense will be in English. A zoom link is provided below.\n\nBest wish
 es\,\n\nNina\n\nTitle:\n\nEvolution and Sources of Switchbacks Observed in
  the Solar Wind\n\nAbstract:\n\nRecent observations by the Parker Solar Pr
 obe (PSP) mission\, launched in 2018\, provide\n\nnew clues on the origin 
 of the solar wind. The scientific goal of the mission is to reveal\nthe ph
 ysical mechanisms closest to the Sun that are linked to two fundamental an
 d\nunresolved questions\, the problem of heating and acceleration of the s
 olar wind. The\nmission revealed the ubiquity of sudden deflections of the
  solar wind's magnetic field\,\nknown as switchbacks. These structures\, w
 hich propagate at the Alfvén speed\, could\nbe the source of energy trans
 fers that answer these questions. Their origin and their\nability to survi
 ve in the solar wind have yet to be elucidated.\nThe work carried out in t
 his thesis aims to understand the origin and evolution\nof switchbacks bas
 ed on both in situ magnetic field measurements and remote sensing\nobserva
 tions. First\, I focus on the nature of switchback boundaries\, the interv
 als that\ninclude most of the magnetic field deflection. Due to the comple
 x 3D structure of these\nboundaries\, their analysis requires the definiti
 on of a new methodology. I show that\nthe nature of the boundaries corresp
 onds to closed structures\, which is a new result.\nThis has an implicatio
 n on the propagation of switchbacks\, as the results suggest that\ntheir e
 rosion may be much slower than expected. This\, in turn\, may explain why\
 nwe observe switchbacks far from the Sun. The results are also compatible 
 with an\norigin of switchbacks that is rooted in the lower solar atmospher
 e\, which motivates\nthe second part of my thesis. There are various non-e
 xclusive hypotheses as to the\norigin of switchbacks\, including an origin
  in the Sun's lower atmosphere. Nevertheless\,\nthere is currently a conse
 nsus on the role that small reconnection events play in the\nSun's lower c
 orona in creating conditions for generating switchbacks through magnetic\n
 reconnection. This hypothesis has yet to be verified due to the difficulty
  of relating\ntransient events in the corona with structures propagating i
 n the solar wind. The\naim of this study is to establish\, statistically a
 nd through observations\, whether jets\nfrom coronal bright points located
  in coronal holes can be precursors of switchbacks.\nAlthough this study i
 s the most detailed approach to date\, the results show no clear\ncorrelat
 ion. Different reasons are considered. The implemented models would not be
 \nprecise enough to study the small-scale eruptive events\, that would req
 uire a finer\nanalysis of the magnetic topology in the lower corona. Evolu
 tionary changes during\nsolar wind propagation could affect our findings. 
 It could also mean that a wider range\nof eruptive events\, not just jets\
 , might be the precursors of switchbacks.\n\nComposition of the jury:\n\nA
 LEXANDROVA Olga\, Rapportrice\, Observatoire de Paris/LESIA\nPATSOURAKOS S
 piros\, Rapporteur\, Université d'Ioannina\nLE CONTEL Olivier\, Examinate
 ur\, LPP\nVAN DRIEL-GESZTELYI Lidia\, Examinatrice\, MSSL -- UCL\, Konkoly
  Observatory\nWILSON Lynn\, Examinateur\, NASA/GSFC\nDUDOK DE WIT Thierry\
 , Directeur de thèse\, Université d'Orléans\nFROMENT Clara\, Co-encadra
 nte\, LPC2E\, Orléans\n\nZoom link:\n\nhttps://us02web.zoom.us/j/87830623
 594?pwd=bA1cfSbhDZnopWOjjQbf4cAOUjXTLy.1\n\nMeeting ID: 878 3062 3594\nPas
 scode: 291310
CATEGORIES:Séminaires et soutenances de thèse/HDR
LOCATION:LPC2E\, 3 Av. de la Recherche Scientifique\, Orléans\, 45071\, Fr
 ance
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 tifique\, Orléans\, 45071\, France;X-APPLE-RADIUS=100;X-TITLE=LPC2E:geo:0
 ,0
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DTSTART:20241027T020000
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